The invention relates to a method and device for conveying at least one filled sack from a suspended position at an individual filling nozzle into an upright position on a running conveyor belt for introduction into a sack closure device. In the method, the travel speed of the conveyor belt corresponds to the closure speed of the sack closure device. In the device, a clamp arrangement includes two approximately vertical arms, jointed and capable of swivelling, with clamping strips. Each clamping strip extends in the direction of the aperture edge of the sack. The arms are capable of moving in order to clamp the sack flap via the clamping strips beneath the filling nozzle by way of the closure of the clamping strips. A linear drive unit moves the clamping arrangement horizontally in the direction of the conveyor belt. A lifting unit raises and lowers the clamping arrangement. A device spreads and fits sacks onto a filling nozzle, especially flat sacks with simple flap lateral folds or of lateral fold sacks with multiple lateral folds. The sack aperture extends at one of the ends over the width of the sack. The sacks are arranged individually with the opened sack aperture pointing forwards. A pair of spreading paddles are secured to first swivel arms. The spreading paddles are capable of being introduced into the sack aperture in the vicinity of the lateral folds. The first swivel arms are capable of swivelling about a horizontal first swivel axis located above the sacks. The spreading paddles are arranged so as to be capable of swivelling about a further horizontal swivel axis which lies parallel to the forementioned first swivel axis. The spreading paddles are attached to shorter second swivel arms on a smaller radius in comparison with the first swivel arms, which, in turn, are capable of swivelling. A pair of sack grabs grasp the two lateral folds in the area of the sack aperture. Swivel arms are provided for the sack grabs which are capable of swivelling about the same horizontal first swivel axis located above the sack as the first swivel arms for the spreading paddles.
A method and a device are known from DE 92 03 380 U1. Here, sacks are filled in a suspended position at a filling nozzle and are grasped by horizontal clamping strips. After release by sack clamps arranged at the filling nozzle, the sacks are placed on a conveyor belt running beneath the filling nozzle. The sacks are first secured at that point against opening or falling over, and are then cleared for movement. In this situation, the possibility is provided of the sack aperture being grasped and closed by means of a clamping strip even before release by the sack clamps arranged at the filling nozzle. The sacks are conveyed into the sack closure device in a fully closed position which reliably avoids the possibility of the sack aperture springing open.
A problem arises here in that the travel speed of the conveyor belt must correspond to the intake speed of the sack closure device. Also, the horizontal transport speed of the sack is relatively low. The synchronized movement of the clamping arrangement, with which the sacks are held closed and secured against falling over on the conveyor belt, must also correspond with the travel speed of the conveyor belt. By contrast with the closure device, the filling unit operates on a discontinuous basis. Until the clamping arrangement has moved horizontally out of the area beneath the filling nozzle, it is impossible for another sack to be fitted onto the filling nozzle.
As a result, with discontinuous fitting and filling operations at the filling nozzle, a period of "dead" time which cannot be utilized occurs at the filling nozzle. During the "dead" time, it is not possible for another sack to be fitted onto the filling nozzle which has already emptied and been reclosed.
This disadvantage arises in particular with such devices in which two filling nozzles are arranged next to one another. Here, two sacks can be fitted in synchrony with corresponding parallel fitting devices. The sacks are then laid in synchrony on a common conveyor belt after filling and are conveyed in the same direction into a single sack closure device. In this situation, the waiting time until the next synchronized fitting operation of further sacks is increased due to the fact that one of the two sacks must not only move out of the area beneath the corresponding filling nozzle, but must also run in its entirety past the adjacent filling nozzle of the other sack, before the two fitting devices can again be used for fitting two following sacks.
A second device is known from DE 41 41 253 A1. With this device sacks are initially drawn backwards out of a sack magazine. Here, the closed sack base is located forwards in the conveying direction. The sacks are then drawn forwards. The sacks are then drawn onto an alignment table with the conveying direction reversed with the sack aperture facing forwards. The sack aperture is then opened at that point by suction devices capable of being moved apart from one another. The alignment table and the suction means are in a fixed arrangement in relation to the device. The device also includes the means for spreading and fitting the sacks onto the filling nozzle.
Double-action pneumatic cylinders are used as the drive means for the first swivel arms of the spreading paddles and for the further swivel arms of the sack grabs. In order to ensure the precise positioning of the sack grabs in relation to the aligned sacks, on the one hand, and in relation to the sack supports, on the other, this situation requires the first swivel arms for the spreading paddles and the second swivel arms for the sack grabs, respectively, to travel against spring-loaded stops. Both the pneumatic cylinders with the corresponding control elements, as well as the stops, represent relatively expensive components. In view of the fact that high acceleration and speeds are required for the swivel means, this arrangement requires the stops to absorb a considerable impact pulse. Substantial wear is incurred at the stops, and in particular at the corresponding rubber surface pads. The result is replacement at relatively short intervals. A further disadvantage during operation is the considerable noise which is incurred as the swivel means strike against the stops.